(587bg) Silver Nanoparticles Without Metal: A New Generation of Environmentally Benign Anitimicrobials

Authors: 
Velev, O. D., North Carolina State University
Richter, A. P., North Carolina State University
Paunov, V. N., University of Hull
Stoyanov, S., University of Wageningen



Engineered nanoparticles are in use or being considered for use across a wide range of products. One of the most widely used classes of nanomaterials today is the silver nanoparticles (AgNPs), which possess antimicrobial, antisporal and antifungal action. However, lingering concerns about the potential health hazards of nanoparticles and their accumulation in the environment have limited the expansion of nanoparticle technology. Thus the application of Ag nanoparticles has been problematic due to their relatively large cost and growing concerns about the environmental and human dangers of the persistent nanoparticles. We will report the results of the development and testing of a novel class of functionalized, environmentally-benign, nanoparticles (EbNPs) as highly efficient microbicidal substitutes of the AgNPs. These particles are made of biodegradable and environmentally benign biopolymers such as lignin, and are infused with optimal amount of silver in the form of adsorbed Ag+ ions. The active Ag+ ions are released during the targeted adsorption of the surface-modified particles onto bacterial membranes. We will report means of synthesizing such EbNPs in a simple, inexpensive, and non-toxic way, by applying green synthesis methods such as water-based acid precipitation, or by employing solvent exchange precipitation method on modified lignin, e.g. Indulin AT and High Purity Lignin. Dynamic light scattering is employed to measure EbNP size distributions as a function of the operating parameters such as pH drop magnitude, initial lignin loading in stock solution, and choice of solvent. EbNPs with diameters ranging from 40 to 200 nm with pH stability ranging from pH 4.0 to 9.0 were obtained. We have shown that the bactericidal action of these silver-loaded, surface-functionalized particles exceeds the one of the common Ag nanoparticles, and that the new EbNPs kill a broad spectrum of pathogenic microbes. Comprehensive bioactivity studies aimed to evaluate the biotoxicity and the environmental impact of these EbNPs are under way in collaboration with the U.S. Environmental Protection Agency.